LOS ANGELES - Prompted by the discovery of a mountain lion known as P-22 in L.A.'s Griffith Park, wildlife advocates say now is the time to build a wildlife passageway over the 101 freeway.

When it was built in the late 1950s, few planners were aware the route through Liberty Canyon was one of Southern California's most important wildlife corridors, linking the Simi Hills to the Santa Monica Mountains. Over the years, the area has been the site of dozens of tragic collisions between motorists and animals.

Beth Pratt, California Director of the National Wildlife Federation, says mountain lions, bears, bobcats and other wildlife need large areas of habitat to survive and L.A.'s maze of freeways has hemmed large animals into smaller and smaller areas.

"National Park Service scientists have been looking at this issue," she says. "They've collared over 30 cats, and they're getting a pretty good idea of how they move. They've been able to identify this pinch-point on the 101 freeway. They have over 60,000 GPS points showing three mountain lions going up to the 101, and turning around."

But some mountain lions do try to cross at Liberty Canyon, and elsewhere along the 101, and many are hit and killed - similarly endangering drivers.

Pratt says major highways like the Ventura Freeway are a challenge not only because mountain lions keep getting hit by cars, but the abundance of freeways also leads to reduced genetic diversity, and even inbreeding among wildlife in the region.

She says with such an extraordinary amount of urbanization along on the edge of wildlands in Los Angeles, wildlife crossings are one way the damage done to wildlife populations can begin to be repaired.

"What it's really doing is restoring balance to an ecosystem that, because of these freeways cross-cutting it, is not there right now, " she says. "You have animals existing on islands of habitat and that's not good for the Santa Monica Mountains as a whole."

While the design is expected to mirror similar projects already built in the Netherlands, Banff National Park in Alberta, and on the Flathead Reservation in Montana, the Los Angeles crossing has the potential to be the largest wildlife crossing in the world.

"For L.A., that would just show wonderful leadership," says Pratt. "L.A. is sometimes unfairly tagged as a bad environmental player, but if L.A. were to become the site of the largest wildlife crossing in the world - what a statement."

Pratt notes the active and supportive involvement of the California Department of Transportation has been a significant factor in moving the proposed crossing project forward.